scholarly journals The spatial coherence wavelets and second-order correlation

2015 ◽  
Vol 9 (1) ◽  
pp. 1-6
Author(s):  
Juan González ◽  
Román Castañeda
Keyword(s):  
Spatial Coherence ◽  
Second Order

scholarly journals Optical coherence encryption with structured random light

PhotoniX ◽  
2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Deming Peng ◽  
Zhaofeng Huang ◽  
Yonglei Liu ◽  
Yahong Chen ◽  
Fei Wang ◽  
...  
Keyword(s):  
Fractional Fourier Transform ◽  
Spatial Coherence ◽  
Second Order ◽  
Statistical Characteristics ◽  
Interference Effects ◽  
Complex Environments ◽  
Optical Encryption ◽  
Light Matter Interaction ◽  
Encryption Method ◽  
Promising Avenue

AbstractInformation encryption with optical technologies has become increasingly important due to remarkable multidimensional capabilities of light fields. However, the optical encryption protocols proposed to date have been primarily based on the first-order field characteristics, which are strongly affected by interference effects and make the systems become quite unstable during light–matter interaction. Here, we introduce an alternative optical encryption protocol whereby the information is encoded into the second-order spatial coherence distribution of a structured random light beam via a generalized van Cittert–Zernike theorem. We show that the proposed approach has two key advantages over its conventional counterparts. First, the complexity of measuring the spatial coherence distribution of light enhances the encryption protocol security. Second, the relative insensitivity of the second-order statistical characteristics of light to environmental noise makes the protocol robust against the environmental fluctuations, e.g, the atmospheric turbulence. We carry out experiments to demonstrate the feasibility of the coherence-based encryption method with the aid of a fractional Fourier transform. Our results open up a promising avenue for further research into optical encryption in complex environments.

Second-order temporal and spatial coherence of thermal electrons

1987 ◽  
Vol 99 (2) ◽  
pp. 227-245 ◽  
Author(s):  
M. P. Silverman
Keyword(s):  
Spatial Coherence ◽  
Second Order ◽  
Temporal And Spatial

Spatial coherence of light and a fundamental discontinuity of classical second-order wave fronts

2013 ◽  
Vol 88 (3) ◽  
pp. 035401 ◽  
Author(s):  
Román Castañeda ◽  
Esteban Franco ◽  
David Vargas
Keyword(s):  
Spatial Coherence ◽  
Second Order ◽  
Wave Fronts

Disappearance Voltage Determinations Using a Convergent Beam

1971 ◽  
Vol 29 ◽  
pp. 184-185
Author(s):  
W. L. Bell
Keyword(s):  
Second Order ◽  
Objective Method ◽  
Uniform Thickness ◽  
Rocking Curve ◽  
Crystal Perfection ◽  
Kikuchi Line ◽  
Central Maximum ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Technique

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

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